Effects Of Partial Substitution Of Nitrogen Fertilizer On Soil Characteristics And Millet Yield And Quality

Millet is one of the main characteristic grain crops in the Loess Plateau of Inner Mongolia,and there are problems such as low nitrogen fertilizer utilization rate and low yield and instability in production.In this study,through a two-year field experiment,on the basis of consistent total fertilization nutrients,conventional fertilization（NPK）was used as the control,and a total of four fertilization treatments were set up,namely bio-organic fertilizer（N+BM）,rotten sheep manure（N+SM）and slow-release urea（N+HM）to replace 20%of the total nutrients of nitrogen fertilizer and no nitrogen fertilizer treatment（PK）.The effects of substituting some nitrogen fertilizer with different fertilizers on millet growth and development,soil nutrient change,yield and quality formation,and nitrogen fertilizer use efficiency were explored,which provided a theoretical basis for guiding the scientific fertilization and high yield and quality of regional millet.The main results are as follows:1.Nitrogen substitution had a greater effect on millet stem thickness and leaf area,but had a small effect on plant height,among which N+SM was the most obvious.From the rough view of stems,the N+SM treatment at the ripening stage increased by 5.66%compared with the control,and the N+BM increased the dry matter accumulation by5.16%～11.45%compared with the control.The net photosynthetic rate of N+BM treated leaves in the grouting stage was 18.69μmol H₂O/（m²·s）,which was the highest among all treatments,and increased by 16.25%compared with the control.The data of the two years showed that the SPAD values in the panicle stage and the grouting stage increased by 1.03%～13.29%compared with the control.2.Nitrogen fertilizer substitution can increase soil nutrient content.The total nitrogen content of soil in the 0～40 cm soil layer in the mature stage showed the highest N+BM(0.55g·kg^-1),which increased by 12.24%compared with the control.N+BM,N+SM and N+HM treatments could significantly increase the contents of alkaline hydrolyzable nitrogen,ammonium nitrogen and nitrate nitrogen in the filling and mature stages,while N+HM treatment had no significant effect on soil organic matter content.The urease content in soil layer 0～40 cm was the highest in N+BM treatment at the ear stage,which increased by 5.14%compared with the control.The N+SM treatment of soil microbial biomass nitrogen content was optimal among the treatments,which was22.17%higher than that of the control.3.Nitrogen fertilizer substitution can increase millet yield and quality.The yield of N+BM was 4985.49kg/hm²,which was 16.95%higher than that of the control.N+SM treated with the highest crude fat content（3.67%）,which increased by 6.04%compared with the control.N+SM treatment had the lowest total starch content,which decreased by6.84%compared with the control.4.Nitrogen fertilizer substitution can improve nitrogen fertilizer utilization efficiency.The accumulation of nitrogen in N+BM treatment increased significantly,which was 8.41%higher than that of the control.The productivity and agronomy utilization rate of nitrogen fertilizer in N+BM treatment increased significantly,with an average increase of 11.19%and 63.12%compared with the control.The apparent utilization rate of nitrogen fertilizer treated by N+BM was 36.18%,which was 35.47%higher than that of the control.Combined with the growth characteristics of millet and local soil basic fertility,compared with conventional fertilization,bio-organic fertilizer,rotted sheep manure and slow-release urea replaced nitrogen fertilizer by 20%of the total nutrients promoted crop growth,improved soil nutrients,increased millet yield,improved nutritional quality,and improved millet nitrogen use efficiency.It is suggested that bio-organic fertilizer replace20%of the total nutrients of nitrogen fertilizer as a fertilization mode for millet to increase quality,stable yield and efficiency in the Loess Plateau of Inner Mongolia.